The invention relates to a carburetor arrangement in a housing including the housing of a work apparatus such as a motor-driven chain saw, brushcutter or the like.
Known carburetor arrangements are built up in such a way that the carburetor with an intake air filter is attached to a housing partition wall which is arranged between the internal combustion engine and a carburetor space. In this way, a too intense heating of the carburetor is intended to be countered. The connection between the carburetor and the inlet channel of the engine is via a connecting pipe which, for example, can be configured as an elastic connecting stub. The connecting pipe is mostly made of a material having a poor thermal conductivity in order to prevent a thermal bridging as much as possible. Notwithstanding the known measures, a damaging heating of the carburetor cannot be completely precluded under unfavorable operating conditions because of the ever smaller and tighter housings. However, if the carburetor becomes too hot, this can lead to the formation of vapor bubbles which negatively affect the operation of the engine. For example, if a work apparatus, which is equipped with an engine, is switched off after an operating cycle, the carburetor can warm to the point where vapor bubbles are formed thereby greatly hindering a restart of the engine.
It is an object of the invention to provide a carburetor arrangement of the kind described above which is improved so that a damaging warming of the carburetor is reliably avoided during operation of the engine as well as after an operating cycle.
The carburetor arrangement of the invention is disposed in a housing accommodating an internal combustion engine having an inlet channel. The carburetor arrangement includes: a carburetor defining an intake channel; a connecting pipe connecting the inlet channel of the engine to the intake channel of the carburetor; the carburetor having a front end facing away from the connecting pipe; an air filter assembly for supplying combustion air to the engine; the carburetor having a contour and being connected to the air filter assembly at the front end; and, a heat-draining component mounted on the front end and projecting beyond the contour.
By mounting the heat-draining component at a location lying remote from the engine, a significant quantity of heat can be conducted away via a thermal-conducting contact with the carburetor so that a damaging warming of the carburetor itself is avoided. The heat-draining component projects beyond the contour of the carburetor so that these sections, which project beyond the contour, can give off heat advantageously on both sides over a large area. In this way, a cooling body is provided with which a formation of vapor bubbles in the carburetor can be reliably avoided even under unfavorable conditions.
Preferably, the heat-draining component is mounted on an end face of the carburetor and is especially clamped between the carburetor and the air filter case. In this way, a heat-conducting contact to the heat-draining component is established on the entire end face of the carburetor in order to achieve a large-area thermal transfer into the cooling body. This cooling body is preferably configured to be three-dimensional so that every possibility for conducting heat away in all axial directions of the space can be utilized.
It is practical to configure the heat-draining component so that a bent-over, wing-shaped cooling flange lies at a lateral distance next to the carburetor. In this way, also the dead spaces can be utilized for cooling the carburetor itself. The cooling flange lies advantageously in a space between the carburetor and the air filter case and is preferably at a spacing to the air filter case.
In a further embodiment of the invention, the heat-draining component is provided with a receiving pocket which engages under a housing section of the air filter case. The housing section of the air filter case lies essentially without play in the receiving pocket in the direction of the longitudinal center axis of the carburetor. The end wall of the receiving pocket is preferably attached to the housing section of the air filter case. In this way, the heat-draining component and the air filter case are connected to an assembly component utilized together. It can also be advantageous that the heat-draining component be placed in the injection mold of the air filter case manufactured usually of plastic so that the heat-draining component is fixedly connected to the air filter case.
In a preferred embodiment of the invention, the heat-draining component is made of heat-draining sheet metal and this sheet metal is preferably bent over several times. In a first manufacturing step, a sheet metal plate can be punched. With the stamping operation, not only the outer contour of the heat-draining component can be determined but, simultaneously, the openings can be introduced which are necessary for the attachment and the intake air flow. After this premanufacture of the sheet metal plate, the plate is bent over, for example, at only three bending lines in order to obtain, as an end product, a three-dimensional heat-draining component for arrangement between the air filter case and a carburetor.